"Such figures are used as ammunition by those who believe in the dangers of acquisitions and high market share. These critics believe that Standard’s growth and its ability to acquire so many companies so quickly “must have” come from some sort of “anticompetitive” misconduct—and they point to Standard Oil’s participation in two cartels during the early 1870s as evidence of Rockefeller’s market malice.

The growing success of Standard did not flow from these attempted cartels—neither of which Standard initiated, and both of which failed miserably in very short order—but from the company’s enormous productive superiority to its competitors, and from the market conditions whose groundwork had been laid in the 1860s. Without understanding these conditions, one cannot understand Rockefeller’s exceptionally rapid rise." - The Objective Standard

By the end of the decade, Standard Oil had achieved a 90 percent market share.